#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    bool vis[300][300];
    int dx[4] = { 0,0,1,-1 };
    int dy[4] = { 1,-1,0,0 };
    int m, n;
    int ret;
    using PII = pair<int, int>;
    int numIslands(vector<vector<char>>& grid) {
        m = grid.size(), n = grid[0].size();
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (grid[i][j] == '1' && !vis[i][j])
                {
                    bfs(grid, i, j);
                    ret++;
                }
            }
        }
        return ret;
    }
    void bfs(vector<vector<char>>& grid, int i, int j)
    {
        queue<PII>q;
        q.push({ i,j });
        vis[i][j] = true;
        while (q.size())
        {
            auto [a, b] = q.front();
            q.pop();

            for (int k = 0; k < 4; k++)
            {
                int x = dx[k] + a, y = dy[k] + b;
                if (x >= 0 && x < m && y >= 0 && y < n && !vis[x][y] && grid[x][y] == '1')
                {
                    q.push({ x,y });
                    vis[x][y] = true;
                }
            }
        }
    }
};